Knot tying generally requires inserting one end of a wire or string through a loop formed in the wire to create a knot. Handling of the wire or string during the knotting process can be relatively complex—particularly when the wire or string has a small diameter. Automated knot tying apparatuses have used robotic means where the wire or string being knotted is held and released at different points during the knotting process.
As is known in the art, a surgeon's knot is a simple modification of a reef knot. The surgeon's knot adds an extra twist when tying the first throw, which results in forming a double overhand knot. In practice, the additional turn provides more friction and can reduce loosening while the second half of the knot is tied. This additional integrity to the knot is an important feature in the surgical setting. This knot is commonly used by surgeons in situations where it is important to maintain tension on a suture.
Devices such as hormonal or copper intrauterine devices (IUD), which are used as a common method of anti-conception and/or for treatment of menorrhagia, have a string attached to the device. After insertion of a T-shaped IUD, the string remains positioned within the cervix for a period of 3 to 10 years to facilitate extraction of the IUD by the health care provider. It is customary to provide the string of an IUD with a knot to securely fasten the string. However, to facilitate delivery via an inserter and optimal positioning within the patient's cervix, the knot should be tied so that the knot is not too close or too far from the IUD or does not have a profile exceeding an optimal height. The position of the knot with respect to the IUD and its form and thickness is also important to ensure compatibility with the IUD insertion device and to avoid spreading of possible infectious agents such as viruses, bacteria and fungi from the vaginal region into the uterus, since it has been observed that said knot can be the thriving place of infectious agents. See, for example, Roberts at al., 1984, Contraception 29, Issue 3, pp 215-228; Rivera at al., 1993, Curr. Opin. Obstet. Gynecol. 5(6):829-32). What are needed are devices and methods that facilitate reproducible knotting results.